High-speed digital phase switches for microwave signals have taken a variety of forms. One type of switch changes phase by changing the path length either by removing or including a segment of a transmission line, as by means of a variable resistance. A second type of modulator utilizes a diode bridge which switches current paths at a transformer input. A third type of modulator utilizes dual gate FET switches which pass or block current to alter current paths. Path length modulators do not produce a biphase output if switching elements, such as diodes, are used which have substantial parallel capacitance or series resistance. The presence of series resistance results in an amplitude difference between the transmitted and reflected signals producing the two output states. Because the output phase is affected by the switches' parallel capacitance, it is necessary to use switch elements having a low parallel capacitance such as PIN diode devices. However, the voltage switching time of such diode devices is long. Other types of current path switching circuits experience difficulty at higher frequencies where current routing schemes introduce phase and amplitude shifts.